Two-stroke internal-combustion engine



May 23, 1944. 11 PYK TWO-STROKE INTERNAL COMBUSTION ENGINE Filed June 13, 1940 Fr .1

PRIOR ART y 23, 1944- H. T. PYK 2,349,305

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed June 13, 1940 2 Sheets-Sheet 2 Patented "May 23-, 1944 Herman Theodor :Pyk, 'SaltsjoeDuvnas. Sweden -Application June v13,194t'LSerial No. 340,266 In Sweden .Aprild, 1940 '5 Claims. (01." 123- 32) The present invention rela'tes :to two-stroke internal {combustion zenghiesg-having scavenging air ports 1 and .exhaustmozits :iniit-he cylinder "wall controlled by the ,piston and having further, fuel injecting meansmentrallyidisposed in the cylinder head.

In .order toob'tain .a "favorable combustion and thus -.a high :efiective average pressure, above everything caneffectivesscavenging :of the cylinder and besidesa-iorm :o't the compression chamber-suitable fornthe iniectionand :the combustion is required. y

The invention :will .be elucidated .in connection -withtthe-annexeddrawings, in .which Figs. ,1 and 2 show difierentknow-n.tormsnofithe compression chamber, :whereas Figs. 3 and l .4 show.also diagrammaticallyitwo di-iferentiorms ofa compresrrsionchamberjaccording.to the invention. .Fig. 5 is an axial section along the {111165 55111 Rig. 6 ,andFig. 6 a-crossesection-alongtline 6-4 in Fig. .5 of the cylinder to! tan internal combustion engine ihavi-ng 8, ;so-:called -:oppositely directed scavenging and .a compression .chamber of the formshorvniiniilig.

Ilimall :of .theiflgures, denotes the cylinder, .2 the piston :an dril' the cylinder-head having-a centrallydisposed IuelJinJection 4. The compression orcombust'ionchamber is denoted -byr5.

It is previously known that unimproved utilization o1' .the.;.airatathe combustion can be obtainedby concentrating the volume orsbulk. of the compression chamber torthe aperiphery :t-hereof. .A compression gchamber formed from this point oflviewmay bewholly cylindrical. or theaxialdistancebetweenithemiston:and :the cylinder head may increase ctowards'ithe "periphery, said latter formation being :applied 1 1120 .a greater or less .ex- .tentto; all'of1thezcompression.chambers, shown.

Besideaiin-the embodimentaccording1to.Fig. 1 .the =:compression cham'ber'isbetween "the cylinder head 1 G and i-the-piston i2, :whemthe latter is :in its outer Flimit :position, :iis-sso iformed that voutlnost about the .;periphery there *i-is ,;formed an axially narrovwannulanspace oribdlk-portiont, which is directedperpendicularly?togthecylinder.axisand has. a certain media]; length. i-Besides, towards; the centre the compression chamber is formed by recesses! anda8,",rcspec.tively,=in the piston and in :the 1 cylinder head.

Hera-1th.: recess *1 'inithe 1 piston :has been made with'the, objectfin view ;that the; annular edge at the peripheryof:theipistonzresulting fromsaidrecess shall =prevent ;the.i fuel.. rays ifrom hitting'the cooledzcylinder-wall, -whichtwouldlresult-in alcoh- :densation and precipitation of i-fuel on the said wall. "However, here the direct disadvantageous action has been wholly overlooked, whichoccurs due to the bulk reduction :between the annular faces of;the piston and the cylinder :headiorming the space :6, .when the piston :approachesits outer limit position. The radially inwardly directed air-stream P generated atfthewsaid motion ofthepiston towards'the annular surface at the peripheryof the cylinder "head-will. namely cross the fuel rays, partof the'iuellbeing thereby present above ther-airvstream and pressed against the cylinder head resultingin'aniimperfect-combustion. To this contributes also the condition that thesaidair-streamrrom'the space .6 counter-acts the itroughedriving capabilitygofzthe fuel rays.

In theaembodiment-accordingto Fig.12ithe piston 2 is provided at 'theiperiphery with-an annular conical "surface and the-cylinder head with a correspondingconical surface an annular conical space orbulk portion! being formed betflejen the said surfaces-in the outer-limit position or the piston. The conicallsurface oftthewcylinder 'head 'zextends "towards the centre and may :be :somewhat-curved. .The air-stream Pfoccurrin'g-when in any considerable degree. Furthenthe-airand the duel 'possibly ,aaccompanying it will here -%be cooled, which also combustion.

disadvantageously afl'ects the In thefembodiment-accordingrto Elsie. accesses and 8, respectively,-:are made jinztheipistcnl lgas well as in the cylinder head :3, ais 515119508959 a m the :known. embodiment according ;to "535g. .1. However, in distinction from said ilattenahabcidiment, conical surfaces having 'ga-rceritain iengith and directedzobliquely upwards: towardsithezcentre areihere made atthe 'peripherygof ,thepistcn h d :the cylinder head. so that inthe outer iii-mince .sition-ofzthe piston there:willibeyformedzhetween the said surfaces afi-gobliquely, upwardlyaiiregcted conical space or bulk position 1150. :In

and the conical faces are rounded.

Through the conical facing-otthe piston, which -isrknown.perse, it is obtained that ;the.-scaven ginjg through the; ports in :the cylinder walL- when the piston erably' improved, since by thetsaid ,mean's ithe scavenging :air obtains :assuitable .idirecti-on "Ju wardly'towards the cy1inderfhead -fIhiseaction will be particularly:advantageous:in such-"cases.

where a" so-called oppositely directed scavenging is used, as will be more clearly described below.

A wholly new action, which is obtained by providing the piston as well as the cylinder head with conical facings in combination with recesses at least in, the head, consists in this that, when the piston approaches its outer limit position, the

air present in the annular space It between the 7 piston and'the' head i isiior ced into-the innercom-- pression chamber thereby efiectirigan' airstream P, which is particularly advantageous with respect to the incoming fuel rays.

Hereby, an air-stream is namely obtained, whichis die.

However, according to tests made it has been proved that the said solutions of the problem are incorrect and not suitable for obtaining the best scavenging results. The air is namely much more easily movable than it is generally believed and its tendency of being mixed with the exhaust gases is very great, which according to what has been proved by tests made .prevails particularly in the so-calledieven courses-of strg'ea'rning, which results'inrelatively great remaining whirl formations in separate parts of the combustion chamber, such as powerful vertical whirls prependicurected towards the centre and passes upwards towards the cylinder head and to a great extent, 7

thanks to the recesses 8, will passabov the fuel rays without the risk of being arrested.. Thus, the incoming fuel is forced downwardly by the air-stream, and simultaneously the air-stream.-

also hits and bring with it the fuel rays, which reboundsagainst the cylinder head from the piston.

Thus, bythe said means it is-gained that the fuelwill; be distributed evenly about the whole end .face ot -.the.-='piston. Then; when. the piston moves downwardly and the'expansion takes place, the airgpresent above thefuel will penetrate the fuel =layer;:whereby the combustion is maintained anddntensified.

Inother words, by the said means a more complete-combustion is obtained than in the known forms,.-ot thecombustion chamber, whereby the fuelcconsumption per horse-p'ower-hourwill be reduced..: .-Besides,.a greater quantity of fuel can I be 'completely'bumed, which results-in that the average pressure in 'the cylinder and thus also the effect of the engine can be increased. In theiembodimentaccording to Fig. 3, the surface. "of :the cylinder head inside the 'recesses 8isimacleplanet Il-i'e embodiment according to Fig. 4'"differs from r that" one illustrated in Fig. 3 in this respect 'only'that thesurface ofth'e cylinder head inside the recesses lds' made conical instead of plane.

The action is the same as that 7 one 'of bodimentLaccordingto-Fig. 3. v

Concerning the conical faces of'the piston and the cylinder head it is to be noted 'that'th'eir angle-to-a plane perpendicularto theaxis of the cylinder preferably can lie between 20 to and tha'tthe' radial length of the faces preferably can to 1 5% -'of the diani'eter of the In the construction of working cylinders and pistons-"oi two-stroke internal combustion e gines for sc -called double-directed scavenging it I hashitherto beenpre'sumed that the scavenging air in order to givethe best scavenging action, H

after it' has passed the scavenging ports, so to say ougl e w sweep throu'ghihe cylinder chamber and to shove the combustion gases ahead of'it out through the exhaust ports. It has namely been'thought'to beof importance that the scav engingshouldproceed as continuously and evenly as possible; so 'thatturbulencslandthus.a mixing of scavenging airi and combustion gases should be prevented in the "greatestpossible de-.

gree, Thus, witlrthisj object in'viewthepiston or theicylinderjheadfor both havebeen iformed insuch'a manner that the'deflection of the airstream upwardly as"well as downwardly should be facilitated in everyway and that the air-.

stream should be kept together to the greatest possible extent duringthe passage through the;

cylinder chamber. a

, larly t0 the symmetry plane.

Thereby, large quantities of scavenging air will be forced out through the exhaust ports, whereas the whirl formations," consisting in part of combustion gases will remain in the cylinder, after the piston ,,having covered the exhaust ports. Many attempts have been made in order to get rid of the said whirls by suitable location of certain scav enging ports etc. However, any. really-satisfac tory results have not been;.obtaine-i, and-for this reason the singleedirected;scavengingwith scavenging ports in.the lowerpart otthe cylinder and exhaust valves inathe cylinder head more i and more has been made use 01, a system which,"

though moreexpensivezyet more easily leads to one of the aims, i. -e..to ahigh' .s'cavenging-eili-f ciency.

However, a scavengingottheso-called double directed art ought to have anentirely different course. Thus, it has been proved to be advantageous to throw thescavenging' air upwards towards the upper parts .oi-thecylinder at the 1 greatest possible velocity and with respect to the directionvof movement of theiair stream to make I the cylinder head of such'ashapethat the scavenging air stream be not deflected downwards but instead will be divided and convertedinto' a great numberof smalLwhirl-iormations', which get a tendency of remaining in the upper part of the cylinder and gradually displace the exhaus'tgasesi It is true that. also in this case whirl-formations occur in the layer between the scavenging air and" the exhaust gases, but also here the whirls will be small and graduallydisplaced-by the pure scavenging air, and themixtures will be forced out through the exhaust ports during the last" period of the scavenging process By making an upwardly directed deflection at the inner surfaces of. thecylinder head 'from the" inner peripheryuof theconical facing, ire. by

making a recess in the cylinder head, in combi-' nation. with the conical facingof -the pistonf i't has-been proved that-the above mentionedeven scavenging stream' does not. occur and that the desired stopping up:of the scavenging air 'in the upperpart of the cylinder is obtained. The said result isyattained not cnlywhen-using thecom sionchamberfi isformed in chamber shown 'in-Fig. 4w .1 1

Obviously}. .thescavenging 'a ports ican ar ranged in, other ,mannen. for instance so-thatthe scavengingair substantially will be directed along the cylinder wall opposite-to the exhaust ports or as-well' as a longxthe said wall. 1,

Let e s lPa ent of theUnited :States Of What I claim as new, and desire to secure' by America is? v l In a two-strokeinternal combustion-engine? envelope;

9. cylinderajncluding aiheadfiand having piston---' controlled scavenging :airand exhaust'ports in the wall; thereof,- a fuel injector centrally located in the cylinder head, and a piston including a head reciprocable in said cylinder, the peripheral marginal surfaces of the piston head and the cylinder head being conical to provide an annular frusto-conical clearance space immediately adjacent to the cylinder wall when the piston is at one end of its stroke, said space being inclined radially inwardly toward the head end of the cylinder, the portions of the surfaces of the cylinder head and the piston head immediately adjacent to the inner periphery of said marginal surfaces extending in directions respectively diverging from the imaginery conical envelope obtalned by extending said marginal clearance space radially inwardly towards the axis of the cylinder and the portions of said surfaces inwardly of the first mentioned portions being shaped to provide a combustion chamber of shallow depth in rela-' tion to its diameter extending in open and unobstructed fashion to the inner margin of said conical clearance space and having substantial portions of its volume located on either side of said envelope and immediately adjacent to said clearance space when the piston is at said one end of its stroke.

2. In a two-stroke internal combustion engine, a cylinder. including a head and having pistoncontrolled scavenging air and exhaust ports in the wall thereof, a fuel injector centrally located in the cylinder head, and a piston including a head reciprocable in said cylinder, the peripheral marginal surfaces of the piston head and the cylinder head being conical to provide an annular frusto-conical'clearance space immediately adjacent to the cylinder wall when the piston is at one end of its stroke, said space being inclined radially inwardl toward the head end of the head immediatelyad-jacentto the'inner periphery of the msggmsi surface thereon extending in a direction divergingffrom thei'riiaginary conical -obtainedby extending said marginal,

clearance spacre radiany inwardly-towards the'rzxi's of the cylinder, the portiohsof the surface of the plston'head immediately within'the marginal surface thereon being formed with a depression having walls inclined oppositely to the inclination of said marginal surface and the portions of said surfaces inwardly of the first mentioned portions being shaped to provide a combustion chamber of shallow depth in relation to its diameter extending in open and unobstructed fashion to the inner margin of said conical clearance space and having substantial portions of its volume disposed on either side of said envelope and immediately adjacent to said clearance space when the piston is at said one end of its stroke.

4. In a two-stroke internal combustion engine, a cylinder including a head and having pistoncontrolled scavenging air and exhaust ports in the wall thereof, a fuel injector centrally located inthe cylinder head, and a. piston including a head reciprocabiein said cylinder, the peripheral marginal surfaces of the piston head and the cylinder head being conical to provide an annular 'frusto-conica} clearance space immediately adjacent to the cylinder wall when the piston is at one end of its stroke, said space being inclined radially inwardly toward the head end of the cylinder, the portions of the surfaces of the cylinder head and the piston head immediately adjacent to the inner periphery of said marginal surfaces extending in directions respectively diverging from the imaginary conical envelope obtained by extending said-marginal clearance space radially inwardly towards the axis of the cylinder and the portions of said surfaces inwardly of the first mentioned portions being shaped to provide a combustion chamber of shallow depth in relacylinder, the portions of the surfaces. of the cylinder head and the piston head immediately adjacent to the inner periphery of said marginal surfaces extending in directions diverging from an imaginary conical surface having its apex at said injector and its base at the inner periphery of the marginal surface on said cylinder head and the portions of said surfaces inwardly of the first mentioned portions being shaped to provide a combustion chamber of shallow depth in relation to its diameter extending in open and unobstructed communication with said conical clearance space and having substantial portions of its volume located on either side of said imaginary surface and immediately adjacent to said clearance space when the piston is at said one end of its stroke. v

3. In a two-stroke internal combustion engine, a-cylinder including a head-and having pistoncontrolled scavenging air and exhaust ports in the wall thereof, a fuel injector centrally located in the cylinder head,and a piston including a head reciprocable in said cylinder, the peripheral marginal surfaces of the piston head and the cylinder head being conical to provide an annular frusto-conical clearance space immediately adja-' cent to the cylinder wall when the piston is at one end of its stroke, saidspace being inclined radially inwardly toward the head end of the cyltlon to its diameter extending in open and unobstructed fashion to the inner margin of said conical clearance space and having substantial portions of its volume located on either side of said envelope and immediately adjacent to said clearance space when the piston is at said one end of its stroke, the angle between said conical surfaces and a plane normal to the axis of the cylinder having a value of between 20 and 5. In a two-stroke internal combustion engine, a cylinder including a head and havin piston controlled scavenglhg air and exhaust ports, a

, piston including a head reciprocable in said cylinder, the peripheral marginal portion of the piston head surface being conical and inclined radially inwardly toward the head end of said cylin der to cooperate with the scavenging ports in directing the flow of scavenging air in the cylinder and the portion of the piston head surfaces adjacent to said marginal portion being depressed toward the axis of the piston, the marginal portion of the cylinder head surface being conical to mate with the conical piston head surface and provide a frustro-conical clearance" space immediately adjacent to the cylinder wall when the piston is at one end of its stroke, the portion of the cylinder head surface-immediately adjacent to the conical portion thereof being recessed to diverge from the imaginary envelope obtained by extending said marginal clearance space inwardly toward said axis and the remaining radiall inner portions of said piston and cylinder head surfaces inder, the portions or'thesurface'of the cylinder being shaped to provide a combustion chamber of shallow depth in relation to its diameter extending in open and unobstructed fashion to the inner margin of said conical clearance spaee,'and

a fuel injector lcentrallylocated in said cylinder 5 head, said injector having orifices for directing fuel in a plurality of widely divergent raysgenerally toward said depressed portion of the pieton head surface and on the piston side of said envelope, whereby to cause the fuel to be deflected by said depressed portion of the piston head surface toward the recessed portion of the cylinder -head surface and to be intersected by and mingled with the inwardly directed air envelope ejected from said clearance space before the deflected fuel reaches the immediate "vicinity 04 the cylinder head surface.

HERMAN THEODOR 'PYK. 

